1. Field of the Invention
The present invention relates to a composition for forming a LaNiO3 thin film, which is used for an electrode of a thin film capacitor, a ferroelectric random access memory (FeRAM) capacitor, a piezoelectric element, a pyroelectric infrared detecting element, or the like, with a chemical solution deposition (CSD) method; and a method of forming a LaNiO3 thin film using this composition. Specifically, the present invention relates to a LaNiO3 thin film-forming composition capable of uniformly forming a film having extremely few voids; and a method of forming a LaNiO3 thin film using this composition.
2. Description of Related Art
LaNiO3 (LNO) is known as a material having superior electrical characteristics such as high conductivity and being strongly self-oriented to plane (100). Further, due to its pseudo-cubic perovskite structure, a LaNiO3 (LNO) thin film has superior affinity with a perovskite type ferroelectric thin film and has a small misfit in a lattice constant. Therefore, the LaNiO3 (LNO) thin film is used as a crystal orientation controlling layer when a ferroelectric thin film which is preferentially oriented to (100) plane is formed in a thin film capacitor or the like. In addition, the LaNiO3 (LNO) thin film has a relatively small electric resistance and, as compared to a case where a metal such as Pt is used for an electrode, has superior polarization reversal fatigue characteristics of a ferroelectric film. Therefore, the LaNiO3 (LNO) thin film itself can also be used as an electrode film of a FeRAM capacitor, a piezoelectric element, or the like. Further, due to its translucency, the LaNiO3 (LNO) thin film can also be used as an electrode film or the like of a pyroelectric infrared detecting element. Typically, in addition to a vacuum deposition method such as a sputtering method, the LaNiO3 thin film is formed using a CSD method such as a sol-gel method including: coating a sol-gel solution (composition) in which LaNiO3 precursors are dissolved in a solvent to form a coating film; and baking the coating film at a predetermined temperature to be crystallized (for example, refer to Japanese Patent No. 3079262 (Claim 3, paragraph [0013])).